Conventionally, users have been required to organize multimedia materials, such as image files, video clips, audio clips, and source documents, using tree-like directories with folders (e.g., Microsoft Windows). Nevertheless, recent research has revealed the power of using more flexible, non-hierarchical graphs or networks to organize materials, such as a concept map or semantic network. See, e.g., U.S. Pat. No. 5,506,937, “Concept Mapbased Multimedia Computer System for Facilitating User Understanding of a Domain of Knowledge,” University of West Florida (the “'937 patent”).
However, existing non-hierarchical systems, such as the system described in the '937 patent, have not adequately addressed the dimension of multiple-user, network-based collaborative authoring and viewing. For example, the '937 patent fails to provide simultaneous multi-user viewing and editing, restricted-access user privileges, and shared network libraries and resources. Moreover, it is desirable that such capabilities are provided in a light-weight, platform-independent software environment while incorporating an intuitive, informative, and well-integrated user interface.